The present invention relates generally to a system and method for remediation of soil and groundwater and, more particularly, to a system and method for nitrification/denitrification of groundwater to remove undesirable elements from soil and groundwater.
Disposal practices and handling of nitrogen compounds in industrial and agricultural operations often give rise to undesirable elements in soil and groundwater. In particular, it is possible for soil and groundwater to contain various forms of nitrogen contaminants that require remediation.
When in the environment, organic nitrogen slowly converts to ammonia-N and, in turn, further converts to highly mobile nitrate-N. Accordingly, nitrate contamination of groundwater often exceeds the U.S. Environmental Protection Agency (USEPA) drinking water maximum contaminate level (MCL) of 10 mg (as N)/L. This problem is compounded by the fact that nitrate contamination has been linked to the potential formation of nitroso-compounds in the environment, which are known carcinogens. Therefore, remediation of nitrogen compounds to reduce the potential presence of nitrates in groundwater is desirable to treat contaminated sites and protect clean groundwater supplies.
In the wastewater industry, the reduction/destruction of nitrogen compounds often include physico-chemical processes such as air stripping, breakpoint chlorination, ion exchange, or the like. However, these physico-chemical nitrogen treatment processes have often been found to be either ineffective or inefficient for destroying the various form of nitrogen, particularly under subsurface conditions.
For example, processes that use air stripping to remove contaminants from groundwater are ineffective at removing various nitrogen compounds. That is, while air stripping processes have been successful in reducing some contaminants, such processes are only effective for the removal of volatile compounds and, thus, cannot remove various nitrogen compounds.
Additionally, biological nitrification and denitrification processes have been utilized with some success. These biological processes generally work well in above-ground settings because they require a very specialized process condition for effective treatment. On the other hand, in the subsurface environment, the biological process of nitrification-denitrification is extremely slow because the prevailing conditions are far from ideal for the essential microorganisms to thrive.
As such, some systems have been developed that utilize a phosphorus source, such as polyphosphates and trimetaphosphates that encourage indigenous microbes to anaerobically convert nitrate into nitrogen gas within a groundwater source. While such biodenitrification processes can be performed in situ, they are only capable of attacking and reducing nitrates. Therefore, such processes are ineffective at reducing various nitrogen compounds.
Therefore, it would be desirable to have a system and method for the remediation of a variety of forms of nitrogen compounds as well as nitrates in soil or groundwater.